The overall goal of this proposal is to expand the functions and capabilities of the Rat Resource and Research Center (RRRC) to provide biomedical investigators with the rat models, embryonic stem cells, related reagents, protocols and services that will facilitate their research. The RRRC provides a unique repository service to the research community by importing, storing and distributing a large number of rat strains. It assures that valuable models are preserved and made available to interested investigators, allows researchers to satisfy NIH requirements for resource sharing, relieves individual investigators from the burden of animal distribution and ensures that models are maintained with rigorous genetic quality control and health monitoring to promote experimental reproducibility. Recent advances in genome editing technologies that can be used successfully in virtually any species to make targeted mutations (e.g., knock-outs and knock-ins) will facilitat the ability to genetically engineer rats to create new disease models. As a result, the number of rat models and the number of investigators using rat models for biomedical research is likely to increase substantially and the RRRC, as one of the only centralized repositories in the world will continue to serve a critical role for archiving and distributing these new models. To improve repository functions, applied research to optimize methods of sperm cryopreservation and subsequent recovery will be performed. To begin to address emerging awareness of the impact of the microbiome on model phenotype and experimental reproducibility, the RRRC will provide services to assess microbiota as well as conduct research to better characterize the gut microbiota in rats. To expand the broad utility of the RRRC, we propose to increase our fee-for-services in the areas of model generation, characterization, cryopreservation and rederivation. By expanding our services, the RRRC will serve as a much-needed one stop resource for investigators using rats in biomedical research.